The invention is directed to a forming size, method for producing glass fiber strands and the improved glass fiber strands that have a reduced tendency to form gumming deposits when the glass fiber strands are used under high relative humidity conditions.
Glass fiber strands are made from a multitude of fine glass fibers which are formed by being drawn at a high rate of speed from molten glass streams flowing from small openings in a bushing. Since glass fibers easily abrade each other, a chemical size is applied to the fibers to protect the fibers when they are gathered together into a strand and when the strand is further processed. Chemical sizes typically contain a lubricant for the fibers to prevent abrasion of the individual fibers against each other or against glass fiber handling equipment. The chemical size gives the fibers integrity and workability for any standard textile or reinforcement use. If a strand does not have proper integrity, fuzzing occurs during processing operations and eventually the strand will break. After the glass fibers are formed and coated with the chemical size, they are drawn together by a gathering shoe into one or more glass fiber strands. The drawing of the fibers from the bushing is effected by the use of a winder which is also used to wrap the strand on a tube or spool to produce a forming package. The strand on the forming package is placed in an oven to dry or is allowed to air dry to reduce the moisture content of the strand to facilitate removal of the strand from the forming package. The glass fiber strand can be removed from the forming package to produce yarn, twisted strand, according to a conventional textile twisting techniques such as winding strands on a twist frame and collecting them on a bobbin.
The glass strand, yarn or twisted strand so produced can be used in many reinforcement applications. In industrial applications they are combined with other glass fibers and woven into tapes and fabrics. Also, they are used in making non-woven crims for reinforcement of paper, film and foil laminate. They are also used for reinforcing laminates of paper, foil and various combinations of these materials. They are used widely for reinforcement of carton sealing tape and box corner tape. Also, woven fiber glass fabrics and tapes have hundreds of uses. Among the most common are electrical insulation; reinforcement for laminating or electronic panel boards and print circuits; reinforcement of plastics for boats and for automotive and aircraft parts; filtration fabrics for use in the foundry, carbon black and cement industries; control of air pollution; and use in tarpoulins, roofing membranes and air supported structures.
In processing glass fiber strands and producing many of the above mentioned products the strands must pass through machinery guide bars and other orientation devices, for example, in the production of glass fiber reinforced tape, the glass fiber strands are oriented by a meir bar for proper alignment before coming in contact with the tape material. Manufacturers of glass fiber reinforced tape material have encountered difficulty in producing the glass fiber reinforced tape under high relative humidity conditions. Under these conditions the current binders, used on glass fibers to protect them from breaking when the glass fiber strands are handled and manipulated through machinery, has a tendency to leave gummy deposits on guide bars or orientation devices like the meir bar.
The current binders that are used on glass fibers contain carbonaceous lubricants like an aqueous air size including hydrolyzed starch such as dextrinized corn starch with a vegetable oil. The amount of forming size deposited on the glass fiber is usually about 0.7 to about 2 percent by weight based on the weight of the glass. In addition such additives as cationic wetting agents, emulsifying agents, film-formers such as gelatin and polyvinyl alcohol, may be added to the partially or fully dextrinized starch and hydrogenated vegetable oil. Also, since there is usually a long drying period during which the wet starch and oil deposit can act as a base upon which a fungus can grow, a small amount of fungicide is added, possibly along with a disinfectant.
The proportions of starch, oil, and other additives and the types of starch, oil, and other additives in binders have been varied to suit various requirements. For example, in U.S. Pat. No. 3,227,192 (Griffiths) a sized glass fabric and method are disclosed wherein the aqueous size contains as the binder ingredient an amylose containing starch mixture, having an amylose content of about 35 to 45 percent by weight based on total starch content. The mixture is formed by mixing approximately equal portions of a high amylose starch fraction wherein the remainder of starch is amylopectin and of a water repellent low amylose starch fraction wherein the greater portion of the remainder is amylopectin. Also in U.S. Pat. No. 3,615,311 (Ignatius) a starch size composition is disclosed for coating glass fibers, which has greatly improved drying properties. The starch size composition includes a relatively narrow range of a non-crosslinked cationic starch, which is made cationic by attaching a nitrogen or phosphorous having an unshared pair of electrons thereon to a natural starch molecule, and an underivatized starch that is preferably high in amylose where a portion of the granules of which are incompletely burst. Also, in U.S. Pat. No. 3,869,308 (Graham) a method of producing an improved sized glass fiber strand suitable for plastisol coating is disclosed. The starch based forming size used to coat the glass fiber strand contains a starch, the salt of a polyamino-functional polyamide resin and a carboxylic acid, a wax and fatty triglyceride.
It is the object of the present invention to provide glass fiber strand that has a reduced tendency to form gummy deposits on fabricating equipment, mostly on those parts of the equipment which contact the sized fiber strands under high relative humidity conditions by the use of a fiber size composition that is more hydrophobic than conventional fiber size compositions.